MapKit - 当地图放大时,使路线沿街道行进

Question

我编写了简单的应用程序,它在MapKit上的两个位置之间绘制路径.我正在使用Google Map API.我使用了我在网上找到的资源,这里是我用来向Google提出请求的代码:

_httpClient = [AFHTTPClient clientWithBaseURL:[NSURL URLWithString:@"http://maps.googleapis.com/"]];
    [_httpClient registerHTTPOperationClass: [AFJSONRequestOperation class]];
    [_httpClient setDefaultHeader:@"Accept" value:@"application/json"];

    NSMutableDictionary *parameters = [[NSMutableDictionary alloc] init];
    [parameters setObject:[NSString stringWithFormat:@"%f,%f", coordinate.latitude, coordinate.longitude] forKey:@"origin"];
    [parameters setObject:[NSString stringWithFormat:@"%f,%f", endCoordinate.latitude, endCoordinate.longitude] forKey:@"destination"];
    [parameters setObject:@"true" forKey:@"sensor"];

    NSMutableURLRequest *request = [_httpClient requestWithMethod:@"GET" path: @"maps/api/directions/json" parameters:parameters];
    request.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];    
    [operation  setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject){
        NSInteger statusCode = operation.response.statusCode;

        if (statusCode == 200)
        {
            NSLog(@"Success: %@", operation.responseString);
        }
        else
        {
            NSLog(@"Status code = %d", statusCode);
        }
    }
                                      failure:^(AFHTTPRequestOperation *operation, NSError *error) {
                                          NSLog(@"Error: %@",  operation.responseString);

                                      }
     ];

    [_httpClient enqueueHTTPRequestOperation:operation];

这完美无瑕.当我运行这个并试图显示洛杉矶和芝加哥之间的路线时,这是它的样子:

但.当我将地图缩放到街道级别时,这里是路线的样子:

有没有人知道如何在地图缩放时实现我绘制的路线跟随街道？我想路线显示街道的确切路径.我不知道是否需要在Google的请求中添加一些额外的参数.

任何帮助或建议都会很棒.提前谢谢了!

---

[编辑#1:从Google添加请求网址和回复]

从上面的代码创建操作对象后,我的请求URL如下所示:

http://maps.googleapis.com/maps/api/directions/json?sensor=true&destination=34%2E052360,-118%2E243560&origin=41%2E903630,-87%2E629790

只需将该网址粘贴到您的浏览器中,您就会看到Google发送的JSON数据作为我在代码中获得的响应.

---

[编辑#2:解析谷歌的答案并构建路径]

- (void)parseResponse:(NSData *)response
{
    NSDictionary *dictResponse = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableContainers error:nil];
    NSArray *routes = [dictResponse objectForKey:@"routes"];
    NSDictionary *route = [routes lastObject];

    if (route)
    {
        NSString *overviewPolyline = [[route objectForKey: @"overview_polyline"] objectForKey:@"points"];
        _path = [self decodePolyLine:overviewPolyline];
    }
}

- (NSMutableArray *)decodePolyLine:(NSString *)encodedStr
{
    NSMutableString *encoded = [[NSMutableString alloc] initWithCapacity:[encodedStr length]];
    [encoded appendString:encodedStr];
    [encoded replaceOccurrencesOfString:@"\\\\" withString:@"\\"
                                options:NSLiteralSearch
                                  range:NSMakeRange(0, [encoded length])];
    NSInteger len = [encoded length];
    NSInteger index = 0;
    NSMutableArray *array = [[NSMutableArray alloc] init];
    NSInteger lat=0;
    NSInteger lng=0;

    while (index < len)
    {
        NSInteger b;
        NSInteger shift = 0;
        NSInteger result = 0;

        do
        {
            b = [encoded characterAtIndex:index++] - 63;
            result |= (b & 0x1f) << shift;
            shift += 5;
        } while (b >= 0x20);

        NSInteger dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
        lat += dlat;
        shift = 0;
        result = 0;

        do
        {
            b = [encoded characterAtIndex:index++] - 63;
            result |= (b & 0x1f) << shift;
            shift += 5;
        } while (b >= 0x20);

        NSInteger dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
        lng += dlng;
        NSNumber *latitude = [[NSNumber alloc] initWithFloat:lat * 1e-5];
        NSNumber *longitude = [[NSNumber alloc] initWithFloat:lng * 1e-5];

        CLLocation *location = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]];
        [array addObject:location];
    }

    return array;
}

Answer 1

看起来谷歌没有给你所有的点，或者你没有看所有的点。实际上，我期望地标之间有折线，而不仅仅是像您看起来的那样的地标（带有直线）。

• 检查响应中的 DirectionsStatus 以查看您是否受到限制
• 提供 Google 发回的 json 数据。

我不太确定他们使用的墨卡托投影与谷歌使用的投影完全不同。